Based On Herbaceous Resources Preparation And Characterization Of Electromagnetic Shielding Materials

To cope with the increasing serious problems of electromagnetic radiation pollution,It developed the concept of electromagnetically shielded wood composites based on high-value clean and inexpensive herb resources,using Design Surface and Electron-Microscopy(SEM)and Electromagnetic Shielding Analyzers,the electromagnetic shielding material with electromagnetic shielding effectiveness was prepared by using warm-compaction method with the powder of pennisetum as the substrate and nano-CuO powder as the reinforcement.The main tasks completed are as follows:(1)The evaluation methods of electromagnetic radiation and electromagnetic shielding effectiveness are analyzed.It is found that the shielding effect of electromagnetic shielding material is not only related to the composition,structure,shape and forming process parameters of the material,but also the frequency and field source properties of electromagnetic waves.Correlation is considered to be electromagnetic shielding effectiveness when the shielding effectiveness(SE)of a rmaterial reaches 30 dB or more.(2)Pennisetum powders with a particle size of-40 mesh,-60 mesh,and-80 mesh were prepared,and their basic physical properties and process properties were tested.It was found that the particle morphology was long;its particle size distribution was normal;its bulk density,compressibility(compressive density)and formability(compressive strength)increased with the increase of its mesh number.(3)The"herbaceous plant powder/copper oxide composite material"was prepared with-80 mesh n pennisetum"powder as the substrate,and the distribution ratio and main process parameters were optimized by response surface test design and analysis method.It is found that the optimum addition amount of nano-CuO of Pennisetum powder/copper oxide composite is 40wt%,and the optimum forming process parameters are temperature:180°C,pressure:70MPa,and holding pressure:35min;the static of the composite prepared under the optimal distribution ratio and process conditions the flexural strength,elastic modulus and water absorption are 77.4 MPa,8560 MPa and 2.3%,respectively,which are basically consistent with the predicted values,indicating that the selected response surface model is highly practical,and the optimal distribution ratio and main process determined by the response surface method are high.The parameters are feasible and reliable.(4)Based on-80 mesh"pennisetum"powder,at the optimum forming temperature(180 ?)and forming pressure(70 MPa),the effect of nano-CuO content on the electromagnetic shielding effectiveness of " herbaceous plant powder/copper oxide composite material " was studied.It was found that under the optimal process parameters and optimal distribution ratio(40%by weight of nano-CuO content),the electromagnetic shielding effectiveness of the composites was not significantly changed at 60dB when the frequency was greater than 20MHz.In the 20MHz electromagnetic wave environment,when the nano-CuO content is 30wt%,the shielding effectiveness of the prepared composite material can reach 35dB,and it increases with the increase of nano-CuO content;when the nano-CuO content exceeds 40wt%,the shielding performance of the piece has slowed down.(5)Under the optimal process conditions,the electromagnetic shielding patch of the wall with the specification of 600 X 300 X 5mm was prepared according to the optimal distribution ratio,and the shielding effectiveness was slightly better than that of the test piece.